Two things blend together to make RAID more powerful than ever: An increasing number of die-hard, PC-loving speed- freaks and an ever-decreasing price of the hard drive. We\’re (for most of us) beyond the stage of thinking our hard drives are too small. We\’re beyond the stages of making due because a hard drive costs so much. But, for the PC enthusiast, we\’re not beyond the stage of saying, \”Damn, that hard drive is too slow!\”.
There is where RAID comes in. Individually, most hard drives today are too slow. Regardless of how fast they are designed to be, with the speed of today\’s processor and other system components, hard drives today are a source of incredible bottleneck for a system. With RAID, we can blend the power of two or more hard drives together to accomplish great things.
What is it?
RAID stands for Redundant Array of Inexpensive Disks. This is actually a great name for it. And with the price decreasing like never before, the \”Inexpensive\” part of the name is now becoming a reality. Depending on the setup you choose for your RAID array, it can offer you increased performance by using the power of two hard drives as a single volume or simply using the redundancy of a second drive for increased data security. Just like designers do in mission-critical machines (building redundant systems in case of the failure of one), a RAID array can provide increased security in the event of the failure of one of the drives. I will get into the RAID types in a minute, but any good RAID array will use mirroring technology, meaning that whenever you write something to your primary drive, the RAID setup will simultaneously write the same info to the secondary disk, meaning you always have a duplicate copy. In the event one drive fails, you have an exact, working copy of your entire system on the second disk.
The word \”array\” usually implies a series of elements, each of a similar size and nature. Well, RAID is no different. The optmimum setup for a RAID array employs two identical hard drives. If one of your drives is a 7200 RPM drive, then its best to be sure the other one is also a 7200 RPM drive. The same goes for capacity. If you have one 20 gig drive and the other is a 10 gig drive, your 20 gig drive will only operate on the RAID array as a 10 gig drive. In the example preceding, that RAID array would operate at 5400 RPM if you had a 5,400 RPM drive paired up with the 7200 RPM drive. Summing up, your RAID array will always operate at the speed or capacity of the weakest or smallest drive. A chain is only as strong as its weakest link. So, obviously, if you\’re looking to set up a RAID setup, buy two identical drives.
As you might guess, you need a special controller to set up a RAID array. The controller handles the task of managing read/write requests to both drives, managing the mirroring, etc. On some operating systems, namely NT Server or Win2000, you can use the OS itself as a software-based controller. But, it is always better to install a separate, hardware-based PCI controller. The PCI controller handles all the work onboard, saving the CPU cycles that a software controller would use. Controller cards also come with software to allow you to monitor the status of the array.
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